1. Technical Field of the Invention
This invention relates to a tension device for cables, in particular although not exclusively for application to the handbrakes of automobile vehicles.
2. Prior Art
The handbrakes of vehicles have a lever connected by means of diverse mechanisms to a cable that finishes at a connector, with side lines that extend towards the brake systems situated at the wheels. When the lever is operated, the side lines cause the brakes to be applied, and when the lever is released, the brakes are also released.
The cable that comes from the brake lever often becomes loosened with continuous use and therefore it is necessary to fit tensioning units that maintain the tightness of the cable within pre-set values established by the manufacturer, so that correct braking of the vehicle takes place throughout the service life of the vehicle.
As far as is known by the state of the technique, there is proof of several tension systems applicable to this particular use, most of which are very complicated devices with a high number of constituent items and parts.
The fundamental objective of the present invention is to provide a tension device for cables which is very simple and effective and, moreover, eliminates the risks arising from a relative profusion of components.
Another object of the invention is to provide a tension device for cables which is quite economical to produce.
In order to achieve these objectives, the invention claims a tension device for cables equipped with a, operating lever, a disc with a portion in the shape of a circular sector and another auxiliary portion of a greater extension than the previous one.
The portion of the disc in the shape of a circular sector is mounted on a bushing, on which the brake lever also turns. It is of a certain thickness and has toothing on its circular edge that occupies a certain angle, e.g. 180 degrees.
The other portion starts from the beginning and end of the above mentioned toothed area and extends in a coplanar way to it and reaches a surface area more distant from the centre of the disc.
Prominent on this second portion are, at one end, a flat projection by way of a lug and, at the other end, a wall perpendicular to the surface of the disc that forms a vertical surface and, close to this wall, an also vertically protruding base towards the same side of the disc from which the wall protrudes.
The base is provided to be used as a seating for the end of the cable. As will be described later for the appropriate purposes, and its longitudinal direction forms an acute angle with the longitudinal direction of the wall.
The brake lever is mounted on the same bushing, which in turn is mounted on a support fixed to the vehicle itself, so that the lever turns on the bushing when required to do so by the user.
Situated forward of the disc is a bowl, also mounted on the same bushing. The opening of this bowl is towards the outside, i.e. towards the opposite side to the position of the disc, and its side surface is close to the position of the base of this disc on which the end of the cable is seated, and with the bowl also having a wide circular outer wing, that extends parallel to the lever and above the base and the vertical wall of the disc.
The side surface of the bowl is provided with an annular slot.
The end of the cable that comes from the connector is finished by a small straight cylindrical part with a spherically shaped end of a greater diameter that that of the cylinder, which receives a spring on its exterior.
The cable passes through the interior of the base of the disc, which is U-shaped for example, and the cylindrical finishing part with the spherical portion become situated between the vertical wall of the disc and the outer side surface of the bowl.
The spring rests on the base of the disc and maintains pressure against the spherical portion so as to push this spherical portion against the vertical wall of the disc.
The edge of the brake lever includes a ratchet that protrudes slightly towards the disc, so that its protruding tooth acts against the toothing on the disc.
The stop for the disc makes contact with a support point that holds the central bushing, limiting the anticlockwise travel or turning of this disc.
As mentioned previously, the lever turns on the central bushing secured to the support, the bowl is fixed to the bushing and the disc is enabled to turn on this bushing.
As will be deduced from the description so far, the cylindrical finishing part of the cable, with its. spherical end portion and the spring that is around the cylindrical portion are located in the physical space included between the base and the vertical wall of the disc, the side surface of the bowl and its protruding circular wing, so that the self-tensioning of the cable takes place in this space.
At the beginning of assembly, the tension of the spring that is around the cylindrical part of the finishing part of the cable is studied so that it corresponds to the tension that the cable must maintain in order to carry out its function on the brake mechanisms of the wheels of the vehicle.
In this position, the spherical end of the cable finishing part does not make contact with the vertical wall of the disc and with the side surface of the bowl. Thus, when the lever is turned, the disc turns with it on the central bushing and the ratchet of the lever does not act against the toothing on the disc.
When the cable becomes slacker or loses its pre-set tension due to use, the tension of the spring on the base of the disc becomes greater than the tension of the cable and therefore pushes the spherical portion against the vertical wall of the disc and against the side surface of the bowl, with this spherical portion becoming wedged between both, so that when the lever and the disc are turned, it also causes the disc to turn through a certain angle, as a consequence of which the tooth of the ratchet travels through this angle on the toothing on the disc.
In this operation, the spherical portion of the cable finishing part has also turned through this angle and has obliged the cable to be tightened, until its tension becomes the same as that of the spring of the cable finishing part. When this happens, the spherical portion loses contact with the vertical wall of the disc and with the side surface of the bowl, with the assembly returning to a position similar to its starting position, although with the ratchet housed in the toothing on the disc at a certain angular distance from its initial position.
In these tensioning operations, the disc turns in a clockwise direction, given that in the anticlockwise direction, its protruding stop makes contact with a point on the support.
As the cable again loses tension, the system takes up the slack in a self-tensioning action, with the actions describe being continually repeated and maintaining the correct tension in the cable.
The base of the disc, through which the cable passes and on which the spring of the finishing part of the said cable rests, is very close to the side surface of the bowl, with which the cable that protrudes towards the bowl becomes housed in the annular slot in the bowl after a series of self-tensioning operations of the system have occurred.
The ratchet is provided with a spring that acts against the tooth that the said ratchet is equipped with, so that the ratchet is turned for the resetting of the system by forcing the tooth.
In order to carry out this resetting, the ratchet is used in combination with a cavity cut in the side surface and in the outer wing of the bowl. The ratchet has a lug that protrudes in a perpendicular direction at one clockwise end, which becomes lodged in the previously mentioned cavity.
The cavity in the bowl provides a circular shaped edge at the base of this bowl, and extends at a certain angle of its periphery. From this edge and at the side nearer the lug on the ratchet, the wing has an edge which is not aligned with the theoretical centre of the bowl on which the said lug of the ratchet is supported and slides.
When the lever of the tension device is rotated clockwise, the lug slides on the inclined plane of the edge towards the bottom of the cavity, so that it is pushed by its spring in order to engage the teeth of the ratchet with the teeth of the central body.
On the contrary, when the lever is rotated back counterclockwise to its lowest position, the lug on the ratchet again travels from the bottom of the cavity towards the inclined area, pushing its antagonist spring, until the ratchet is raised and disengages the contact between the teeth of the ratchet and those of the central body, this bringing about the resetting of the system.